April 11, 2021

I, Science

The science magazine of Imperial College

bat eating insect
Not what I had in mind when I said I wanted a cricket bat, but oh well

Agriculture is a costly business. You need seeds to plant, fertilizer to make it grow and machinery to harvest. Unfortunately, we grow most of this food in big, exposed landscapes providing an delicious buffet for billions of insects. It is no surprise, therefore, that pesticide is one of the biggest expenses for British farmers (£720 million in 2009, DEFRA)

This number, however, does not reflect the true amount of pest control that is being carried out in fields around the world. As well as being killed by human action, insects are eaten by

A wide variety of species. In doing so, these insectivorous animals are doing a great service to farmers –  providing an quick, easy and environmentally friendly service for free.  A paper, published in Science, has calculated that bats are worth over $22.9 billion dollars a year in the US alone. For example, a single colony of 150 big brown bats (Eptesicus fuscus) eats nearly 1.3 million insects each year.

By reducing the use of pesticides, the bats have not only saved farmers money. By reducing the amount of pesticide that needs to be released into the environment, the environmental impact of farming is reduced. It also lowers the risk of insects evolving resistance to pesticides.

Bat numbers, however, are dropping in the US at astonishing levels. White-nose syndrome (WNS), caused by a fungus, has killed an estimated one million bats, with some colonies declining by 70%. The fungus infects the skins of bats, and results in the bats depleting the energy reserves too quickly.  WNS has only been observed since 2006 in New York, but has spread rapidly west across the US and Canada.

If that weren’t bad enough, bats are being threatened by wind turbines – a little ironic perhaps considering they were designed to help the natural environment.  It is thought that bats are dying from both direct collisions with the turbines and from lung damage caused by pressure changes in the air around moving turbine blades.

The loss of such a large number of bats is concerning. Ignoring the ecological and environmental implications of losing a vociferous predator in such a large area, bats are a necessary part of our agricultural economy. Even a small investment in monitoring and protecting bat species could save millions of pounds in the long run. In times of economic hardship, such as these, should we not be doing more to help those things in the natural world that help us. It seems only fair.